Field of the Invention
The present invention relates to a method of processing a bonded wafer in which a wafer is bonded to a support plate by cutting off, with a cutting blade, an annular portion of the bonded wafer which extends from the outer peripheral edge of the bonded wafer to a position that is spaced radially inwardly toward the center of the bonded wafer by a predetermined distance.
Description of the Related Art
Semiconductor wafers are processed to have devices such as integrated circuits (ICs), large-scale integration (LSI) circuits, etc. formed on their face sides and demarcated by projected dicing lines called streets arranged in a grid pattern. The semiconductor wafers are then ground on their reverse sides to a predetermined thickness, and thereafter diced along the streets into individual chips by a dicing apparatus. The divided chips are widely used in various types of electronic devices including mobile phones, personal computers, etc. In recent years, chips for use in electronic devices have been required to be reduced in size and thickness in order to meet growing demands for increasingly smaller and thinner electronic devices. In some applications, semiconductor wafers (hereinafter also referred to simply as “wafers”) with a plurality of devices formed thereon may be ground to a thin configuration having a thickness of up to 100 μm.
Generally, a wafer has an outer peripheral edge beveled to an arcuate cross-sectional shape in order to prevent itself from being chipped or emitting dust during its own fabrication process. When such a wafer is ground thin in the manner described above, the beveled portion becomes sharp like a knife edge, tending to allow the outer peripheral edge of the wafer to be chipped, causing damage to the wafer. Accordingly, it has been the general practice to perform an edge trimming process on a wafer before the wafer is ground thin, removing the beveled portion from the wafer along the outer peripheral edge thereof (see, for example, Japanese Patent Laid-Open No. 2003-273053 and Japanese Patent Laid-Open No. 2004-207459).
When the edge trimming process is to be performed on a wafer, it is important to accurately spot the position of the outer peripheral edge of the wafer prior to the edge trimming process. Specifically, the outer peripheral edge and its vicinity of the wafer is imaged from above to capture its image by imaging means (imaging camera), and the position of the outer peripheral edge (hereinafter also referred to as “outer peripheral edge position”) is detected from the captured image. If the outer peripheral edge position of the wafer is detected at three or more locations, then the central position and radius, etc. of the wafer can be determined (see, for example, Japanese Patent Laid-Open No. 2011-249572). The edge trimming process is carried out after the position of the cutting blade has been determined on the basis of the information thus obtained.
In order to improve the handleability of thin wafers or to prevent wafers from being warped and fractured while they are being processed, it has been known to bond a wafer to a support plate thereby to produce a bonded wafer and to handle and process the bonded wafer as a single entity (see, for example, Japanese Patent Laid-Open No. 1992-263425). The bonded wafer includes a wafer, a support plate having essentially the same diameter as the wafer, and an adhesive member bonding the wafer and the support plate to each other. For performing an edge trimming process on such a bonded wafer, the outer peripheral edge and its vicinity of the bonded wafer is imaged from above to capture its image by imaging means (imaging camera), and the outer peripheral edge position of the bonded wafer is detected from the captured image.